var longestCommonPrefix = function(strs) {
    if(strs.length == 0) 
        return "";
    let ans = strs[0];
    for(let i =1;i<strs.length;i++) {
        let j=0;
        for(;j<ans.length && j < strs[i].length;j++) {
            if(ans[j] != strs[i][j])
                break;
        }
        ans = ans.substr(0, j);
        if(ans === "")
            return ans;
    }
    return ans;
};